Frequency response function interpolation for damage detection under changing environment

Damage detection can be carried out based on measured dynamic characteristics of the monitored structure. Several experimental investigations have shown that structural parameters are affected by environmental conditions. This circumstance can lead to erroneous conclusions if damage detection methods based on variations of global structural parameters are applied without properly taking into account this influence. In this paper the sensitivity to changing temperature of a new damage detection method, denoted as interpolation damage detection method (IDDM), is investigated with reference to an experimental example, widely studied by several researchers to check damage detection algorithms: the I40 bridge. Results show that, despite the changes of temperature, the IDDM provides a correct identification of damage location even for cases where the evolution of modal frequencies belies the actual damaged state of the structure. The sensitivity of the IDDM to the joint effect of gradient of temperature and noise in the recorded data is also investigated with reference to a numerical example.